In recent years, network systems, such as WPAN (Wireless Personal Area Network), a sensor network and the like, which use compact and low-power-consumption wireless communication terminals are attracting attention. As another similar system, there is a network system that uses, as wireless communication terminals, active RF tags which emit radio signals by themselves.
These network systems are capable of unifying the management of a large number of wireless communication terminals, so that applications in various fields are expected. For example, in such an application it is expected that wireless communication terminals are attached to respective goods, so that identification, tracking, management, and the like of the goods delivered to a communication area of a management terminal are wirelessly performed. Further, in such an application it is expected that wireless communication terminals are given to schoolchildren, whereby the schoolchildren are wirelessly monitored on their way between school and home by a management terminal installed at a school gate or the like (FIG. 15).
FIG. 15 illustrates an exemplary configuration of a conventional wireless communication system 1500 in which each of a plurality of communication terminals 1520 is authenticated by passing through a communication area of a management terminal (AP) 1510. When an unauthenticated communication terminal 1520 (hereinafter referred to as a terminal STA) enters the AP communication area, the management terminal 1510 detects the terminal STA. The detected terminal STA transmits its own identification information and an authentication request to the management terminal 1510. When determining that the terminal STA can be authenticated, the management terminal 1510 transmits an authentication response to the terminal STA and completes the authentication. The terminal STA for which the authentication has been completed becomes an authenticated terminal ASTA.
FIG. 16 illustrates, for example, an exemplary authentication sequence under IEEE802.15.4 which is a standard for WPAN. In FIG. 16, the communication terminal 1520 transmits an authentication request to the management terminal 1510. When successfully receiving the authentication request, the management terminal 1510 transmits an Ack (Acknowledge; reception acknowledgement) to the communication terminal 1520 and starts authentication processing. When receiving the Ack, the communication terminal 1520 stands by a predetermined time period necessary for the authentication processing. After standing by for the predetermined time period, the communication terminal 1520 transmits a data request to the management terminal 1510. When determining that the communication terminal 1520 can be authenticated, the management terminal 1510 transmits an authentication response to the communication terminal 1520. The communication terminal 1520 transmits, to the management terminal 1510, an Ack for the authentication response. At the time when the Ack for the authentication response is successfully received by the management terminal 1510, the authentication is completed.
The wireless communication terminals used in these networks generally have a low transmission rate (several kbps to several hundred kbps) and a short radio signal transmission range (about several meters to several tens of meters) whereby the communication area of the management terminal 1510 is small. That is, the management terminal 1510 has limited time to spare for each of the moving communication terminals 1520. Accordingly, when a plurality of communication terminals 1520 enter the communication area, a collision between authentication requests, timeout in authentication processing or the like occurs.
For example, FIG. 17A illustrates a state where no problem occurs because a small number of communication terminals 1520 enter the communication area of the management terminal 1510. On the other hand, FIG. 17B illustrates a state where a problem occurs because a large number of communication terminals 1520 enter the communication area of the management terminal 1510. As illustrated in FIG. 17B, when there are a large number of communication terminals 1520, authentication takes a long time to be completed, or authentication fails.
A method is disclosed, as a countermeasure against the above-described collision between the authentication requests, timeout in the authentication processing or the like, in a Patent Literature 1 in which authentication processing is distributed by using a plurality of management terminals.
Citation List
[Patent Literature]
    [PTL 1] Japanese Laid-Open Patent Publication No. 2007-166000